1. Field of the Invention
This invention relates to vehicles which embody multiple ratio transmissions to provide a plurality of operating speeds and more particularly to special purpose and off-the-road vehicles which in some cases require transmissions with a considerable number of ratios to enable the vehicles to operate under a variety of conditions.
2. Description of the Prior Art
Most specialized vehicles for such uses as excavating, earth moving, construction work, material handling and the like utilize a multiple ratio transmission to afford the operator a selection of speed ranges in which he can operate the vehicle. Such transmissions may be manually or power shifted. Such transmissions provide torque multiplication ranging from the largest ratio which provides the greatest torque multiplication to the smallest ratio which provides the least. The speed of the engine normally may be varied by the operator when the transmission is in any of the ratios, but each ratio of the transmission provides a maximum vehicle speed with such maximum speeds being inversely proportional to the torque multiplication provided by the transmission.
Generally speaking the cost of transmissions increases as the number of ratios provided by the transmission increase, and consequently if it is possible to add another operating speed to the vehicle without adding another ratio to the transmission it is possible in many cases to reduce the vehicle cost, and the present invention provides an auxiliary speed control which conveniently adds another speed for a vehicle at moderate cost and without adding another ratio to the transmission.